Method for high-speed spinning of bicomponent fibers

ABSTRACT

Highly crimped, fully drawn bicomponent fibers, prepared by melt-spinning, followed by gas-flow quenching, heat treatment and high speed windup, are provided, as are fine-decitex and highly uniform polyester bicomponent fibers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser.No. 09/708,314, filed Nov. 8, 2000, which in turn is acontinuation-in-part of copending application Ser. No. 09/488,650, filedJan. 20, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for preparing fully drawnbicomponent fibers at high speeds and, more particularly, to a processof extruding two polyesters from a spinneret, passing the fibers througha cooling gas, drawing, heat-treating, and winding up the fibers at highspeeds.

2. Description of Background Art

Synthetic bicomponent fibers are known. U.S. Pat. No. 3,671,379discloses such fibers based on poly(ethylene terephthalate) andpoly(trimethylene terephthalate). The spinning speeds disclosed in thisreference are uneconomically slow. Japanese Patent ApplicationPublication JP11-189923 and Japanese Patent JP61-32404 also disclose theuse of copolyesters in making bicomponent fibers. U.S. Pat. No.4,217,321 discloses spinning a bicomponent fiber based on poly(ethyleneterephthalate) and poly(tetramethylene terephthalate) and drawing it atroom temperature and low draw ratios. Such fibers, however, have lowcrimp levels, as do the polyester bicomponent fibers disclosed in U.S.Pat. No. 3,454,460.

Several apparatuses and methods have been proposed for melt-spinningpartially oriented monocomponent fibers at high speeds, as disclosed inU.S. Pat. Nos. 4,687,610., 4,691,003, 5,034,182, and 5,824,248 and inInternational Patent Application WO95/15409. Generally, in these methodsa cooling gas is introduced into a zone below the spinneret andaccelerated in the travel direction of the newly formed fibers. However,such fibers do not crimp spontaneously and, therefore, do not havedesirable high stretch-and-recovery properties.

An economical process for making highly crimpable polyester bicomponentfibers is still needed.

SUMMARY OF THE INVENTION

The process of the present invention for preparing fully drawn crimpedbicomponent fibers, having after-heat-set crimp contraction values aboveabout 30%, comprises the steps of:

-   -   (A). providing two compositionally different polyesters;    -   (B) melt-spinning the two polyesters from a spinneret to form at        least one bicomponent fiber;    -   (C) providing at least one flow of gas to at least one quench        zone below the spinneret and accelerating the gas flow to a        maximum velocity in the direction of fiber travel;    -   (D) passing the fiber through said zone(s);    -   (E) withdrawing the fiber at a withdrawal speed such that the        ratio of the maximum gas velocity to the withdrawal speed is so        chosen to achieve a specific draw ratio range;    -   (F) heating and drawing the fiber at a temperature of about        50-185° C. at a draw ratio of about 1.4-4.5;    -   (G) heat-treating the fiber by heating it to a temperature        sufficient to result in an after-heat-set contraction value        above about 30%; and    -   (H) winding up the fiber at a speed of at least about 3,300        meters per minute.

Another process of the present invention for preparing fully drawnbicomponent fibers, having after-heat-set crimp contraction values aboveabout 30%, comprises the steps of:

-   -   (A) providing poly(ethylene terephthalate) and poly(trimethylene        terephthalate) polyesters having different intrinsic        viscosities;    -   (B) melt-spinning said polyesters from a spinneret to form at        least one bicomponent fiber having either a side-by-side or        eccentric sheath core cross-section;    -   (C) providing a flow of gas to a quench zone below the        spinneret;    -   (D) passing the fiber through the quench zone;    -   (E) withdrawing the fiber;    -   (F) heating and drawing the fiber to a temperature of about        50-185° C. at a draw ratio of about 1.4-4.5;    -   (G) heat-treating the fiber by heating it to a temperature        sufficient to result in an after-heat-set contraction value        above about 30%; and    -   (H) winding up the fiber at a speed of at least about 3,300        meters per minute.    -   The bicomponent fiber of this invention is of about 0.6-1.7        dtex/filament, the fiber having after-heat-set crimp contraction        values of at least 30% and comprising poly(trimethylene        terephthalate) and a polyester selected from the group        consisting of poly(ethylene terephthalate) and copolyesters of        poly(ethylene terephthalate), having a side-by-side or eccentric        sheath core cross-section and a cross-sectional shape which is        substantially round, oval or snowman.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a cross-flow quench melt-spinning apparatus useful inthe process of the present invention.

FIG. 2 illustrates a co-current, superatmospheric quench melt-spinningapparatus useful in the process of the present invention (as shown inU.S. Pat No. 5,824,248, FIG. 2).

FIG. 3 illustrates an example of a roll arrangement that can be used inthe process of the present invention.

FIG. 4 illustrates a co-current, superatmospheric quench spinningapparatus useful in the process of the present invention, in which twoquench zones are used.

FIG. 5 is a graphical representation of the relationship between fibercrimp contraction (“CC_(a)”) and windup speed for Examples 1 and 2.

FIG. 6 shows a co-current, subatmospheric quench spinning apparatususeful in the process of the present invention.

FIG. 7 is a schematic of another embodiment of a roll and jetarrangement that can be used in the process of the invention.

FIG. 8 illustrates examples of cross-sectional shapes that can be madeby the process of the invention and of fine-denier(decitex) polyesterbicomponent and highly uniform polyester bicomponent cross-sectionalshapes of the invention.

FIG. 9 is a schematic representation of another cross-flow quench systemwhich can be used in the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

It has now been found surprisingly that bicomponent fibers can be spunwith either crossflow, radial flow or co-current flow quench gas,withdrawn, fully drawn, and heat-treated at very high speeds to givehigh crimp levels. It was unexpected that such highly crimpedbicomponent fibers can be prepared in view of the high withdrawal speedsand high draw ratios (that is, high windup speeds).

As used herein, “bicomponent fiber” means a fiber comprising a pair ofpolymers intimately adhered to each other along the length of the fiber,so that the fiber cross-section is for example a side-by-side, eccentricsheath-core or other suitable cross-section from which useful crimp canbe developed. “IV” means intrinsic viscosity. “Fully drawn” fiber meansa bicomponent fiber which is suitable for use, for example, in weaving,knitting, and preparation of nonwovens without further drawing.“Partially oriented” fiber means a fiber which has considerable but notcomplete molecular orientation and requires drawing or draw-texturingbefore it is suitable for weaving or knitting. “Co-current gas flow”means a flow of quench gas which is in the direction of fiber travel.“Withdrawal speed” means the speed of the feed rolls, which arepositioned between the quench zone and the draw rolls and is sometimesreferred to as the spinning speed. The notation “//” is used to separatethe two polymers used in making a bicomponent fiber. “2G” means ethyleneglycol, “3G” means 1,3-propane diol, “4G” means 1,4-butanediol, and “T”means terephthalic acid. Thus, for example, “2G-T//3G-T” indicates abicomponent fiber comprising poly(ethylene terephthalate) andpoly(trimethylene terephthalate).

In the process of the invention, two compositionally differentpolyesters are melt-spun from a spinneret to form a bicomponent fiber.The spinneret can have a design such as that disclosed in U.S. Pat. No.3,671,379. Either post-coalescence (in which the polymers first contacteach other after being extruded) or pre-coalescence (in which thepolymers first contact each other before being extruded) spinnerets canbe used. As illustrated in FIG. 8, side-by-side fibers made by theprocess of the invention can have a “snowman” (“A”), oval (“B”), orsubstantially round (“C1”, “C2”) cross-sectional shape. Eccentricsheath-core fibers can have an oval or substantially roundcross-sectional shape. By “substantially round” it is meant that theratio of the lengths of two axes crossing each-other at 900 in thecenter of the fiber cross-section is no greater than about 1.2:1. By“oval” it is meant that the ratio of the lengths of two axes crossingeach other at 90° in the center of the fiber cross-section is greaterthan about 1.2:1. A “snowman” cross-sectional shape can be described asa side-by-side cross-section having a long axis, a short axis and atleast two maxima in the length of the short axis when plotted againstthe long axis.

Regardless of whether co-current or cross-flow quench gas flow is used,2G-T can be typically heated to about 280° C. for transfer to thespinneret, while the corresponding temperature for 3G-T can be less than280° C., with a transfer holdup time up to 15 minutes.

FIG. 1 illustrates a crossflow melt-spinning apparatus which is usefulin the process of the invention. Quench gas 1 enters zone 2 belowspinneret face 3 through plenum 4, past hinged baffle 18 and throughscreens 5, resulting in a substantially laminar gas flow acrossstill-molten fibers 6 which have just been spun from capillaries (notshown) in the spinneret. Baffle 18 is hinged at the top, and itsposition can be adjusted to change the flow of quench gas across zone 2.Spinneret face 3 is recessed above the top of zone 2 by distance A, sothat the quench gas does not contact the just-spun fibers until after adelay during which the fibers may be heated by the sides of the recess.Alternatively, if the spinneret face is not recessed, an unheated quenchdelay space can be created by positioning a short cylinder (not shown)immediately below and coaxial with the spinneret face. The quench gas,which can be heated if desired, continues on past the fibers and intothe space surrounding the apparatus. Only a small amount of gas can beentrained by the moving fibers which leave zone 2 through fiber exit 7.Finish can be applied to the now-solid fibers by optional finish roll10, and the fibers can then be passed to the rolls illustrated in FIG.3.

Various methods of providing co-current quench gas flow can be used inthe present invention. Referring to FIG. 2 for example, fibers 6 aremelt-spun into zone 2 from optionally recessed spinneret face 3. Using arecessed spinneret face creates a heated “quench delay” space, typicallyidentified by its length. If the spinneret face is not recessed, and ashort cylinder (not shown) is positioned coaxially below the spinneretface, an unheated quench delay space can be created. Quench gas 1, forexample, air, nitrogen, or steam, enters quench zone 2 below spinneretface 3 through annular plenum 4 and cylindrical screen 5. When the gasis air or nitrogen, it can be used for example at room temperature, thatis, about 20° C. or it can be heated, for example to 40° C.; therelative humidity of the gas is typically about 70%. Tube 8, which. atits upper end can be conical as illustrated, is sealed to inner wall 9of plenum 4 and provides the only outlet for quench gas 1 and fibers 6.The pressure of the quench gas introduced into zone 2 and theconstriction provided by tube 8 create a superatmospheric pressure inzone 2, for example in the range of about 0.5-5.0 inches of water (about1.3×10⁻³ to 1.3×10⁻² kg/cm²), more typically about 0.5-2.0 inches ofwater (about 1.3×10⁻³-5.1×10⁻³ kg/cm²). The pressure used depends on thegeometry of the quench chamber and the withdrawal speed of the fiber.The quench gas can be introduced from above, for example, from anannular space around the spinneret, or from the side, as shown in FIG. 2of U.S. Pat. No. 5,824,248. Introduction from the side is preferred toallow better contact of the gas with the fibers for better cooling. Thefibers and quench gas are passed through zone 2 below the spinneret toexit 7, the quench gas being accelerated in the direction of fibertravel due to the constriction of tube 8. The maximum velocity of thequench gas is at the narrowest point of the tube. When a tube having aminimum inner diameter of one inch (2.54 cm) is used, the maximum gasvelocity can be in the range of about 330-5,000 meters/minute. The ratioof maximum gas velocity to the withdrawal speed of the fiber in thepresent invention is so chosen that the fiber can be drawn between thefeed roll and draw roll at a draw ratio of about 1.4-4.5 at atemperature of about 50-185° C. Having been sufficiently cooled by thequench gas to solidify, fibers 6 can then be contacted by optionalfinish roll 10 and passed to the rolls illustrated in FIG. 3.

The process of the present invention can also be carried out with theco-current quench gas flow apparatus shown in FIG. 4. In this process,fibers 6 are melt-spun into zone 2 a from optionally recessed spinneretface 3. A first flow of quench gas 1 a enters first quench zone 2 abelow optionally recessed spinneret face 3 through first annular plenum4 a and first cylindrical screen 5 a. First tapered or conical tube 8 ais connected to first inner wall 9 a of plenum 94 a. The inner diameterof tube 8 a can continually converge as illustrated or can initiallyconverge for a predetermined length and then remain of substantiallyconstant internal diameter. A second flow of quench gas 1 b enterssecond quench zone 2 b through second annular plenum 4 b through secondcylindrical screen 5 b and is combined in the second quench zone withthe first flow of quench gas. Second tube 8 b is connected to secondinner wall 9 b of plenum 4 b. As illustrated, the inner diameter of tube8 b can initially converge and then diverge; but other geometries canalso be used. Quench gas 1 is accelerated in the direction of fibertravel by tubes 8 a and 8 b and can then exit through last exit 7 andoptional perforated exhaust diffuser cone 11. The maximum gas velocityis at the narrowest point of either tube 8 a or tube 8 b, depending onthe gas flows 1 a and 1 b. Fibers 6 pass through quench zones 2 a and 2b, exit the quench apparatus through fiber exit 7, can then be contactedby optional finish roll 10, and then passed around heating, drawing, andheat-treating rolls and jets, for example as illustrated in FIGS. 3, 7,and 9. The pressure used in the first quench zone is typically higherthan that in the second quench zone.

The preparation of bicomponent polyester fibers using quench gas whichis accelerated in the direction of fiber travel by application ofsubatmospheric pressure in the zone below the spinneret is alsocontemplated by the process of the present invention. For example, theapparatus illustrated in FIG. 6 can be used. In FIG. 6, newly formedfibers 6 leave spinneret face 3 and enter quench zone 2. Vacuum source37 pulls quench gas (for example, room air or heated air) into zone 2through perforated cylinders 5 a and 5 b, which reduce turbulence.Optionally, ring 64 can be provided to shield the newly spun fibers fromimmediate contact with the quench gas. Similarly, shield 74 can bepositioned to control quench gas flow. The quench gas and fibers 6 passthrough funnel 8, the gas velocity accelerating as it does so.Additional gas can be drawn in between the bottom of funnel 8 and thetop 39 of tube 35, and optionally gas jets 60 can be arranged to supplystill more gas, especially along the inside of tube 35 to minimize therisk of fibers 6 touching the inside of tube 35. Tube 35 flares outwardat trumpet 58. The shapes of both funnel 8 and trumpet 58 are designedto minimize turbulence. Quench gas velocity is reduced when it enterschamber 43 and further reduced when it enters chamber 49, thus reducingthe risk of turbulence. Perforated cylinder 47 further assists inreducing turbulence. Increased control of quench gas velocity can beattained by various means, for example by use of valve 53, throttle 55,and velocimeter 57. Fibers 6 leave this part of the apparatus throughexit 7, pass by optional finish roll 10, and can then be additionallyprocessed, for example by means of the roll and jet systems illustratedin FIGS. 3, 7, and 9. Optionally, ceramic fiber guides 46 can beprovided at exit 7.

The speed of feed rolls 13 determines and is substantially equal to thewithdrawal speed. When crossflow, radial flow or the like flow of gas isused, the withdrawal speed can be in-the range of about 700-3,500 metersper minute, commonly about 1,000-3,000 meters per minute. Whenco-current quench gas flow is used, the withdrawal speed can be in therange of about 820-4,000 meters per minute, typically about 1,000-3,000meters per minute.

The bicomponent fiber can then be heated and drawn, for example, byheated draw rolls, draw jet or by rolls in a hot chest. It can beadvantageous to use both hot draw rolls and a steam draw jet, especiallywhen highly uniform fibers having a linear density of greater than 140dtex are desired. The arrangement of rolls shown in FIG. 3 is the systemthat was used in Examples 1, 2, and 4 and has been found useful in thepresent process. However, other roll arrangements and apparatus thataccomplish the desired results can also be used (for example, thoseillustrated in FIGS. 7 and 9). Drawing can be done via a single-stage ortwo-stage draw. In FIG. 3, fiber 6, which has just been spun for examplefrom the apparatus shown in FIGS. 1, 2, 4, or 6, can be passed by(optional) finish roll 10, around driven roll 11, around idler roll 12,and then around heated feed rolls 13. The temperature of feed rolls 13can be in the range of about 20° C.-120° C. The fiber can then be drawnby heated draw rolls 14. The temperature of draw rolls 14 can be in therange of about 50-185° C., preferably about 100-120° C. The draw ratio(the ratio of wind-up speed to withdrawal or feed roll speed) is in therange of about 1.4-4.5, preferably about 2.4-4.0. Each of the rollswithin pair of rolls 13 can be operated at the same speed as the otherroll, as can those within pair 14.

After being drawn by rolls 14, the fiber can be heat-treated by rolls15, passed around optional unheated rolls 16 (which adjust the yarntension for satisfactory winding), and then to windup 17. Heat treatingcan also be carried out with one or more other heated rolls, steam jetsor a heating chamber such as a “hot chest” or a combination thereof. Theheat-treatment can be carried out at substantially constant length, forexample, by rolls 15 in FIG. 3, which can heat the fiber to atemperature in the range of about 140° C.-185° C., preferably about 160°C.-175° C. The duration of the heat-treatment is dependent on yarndenier; what is important is that the fiber can reach a temperaturesufficient to result in an after-heat-set contraction value above about30%. If the heat-treating temperature is too low, crimp can be reducedunder tension at elevated temperatures, and shrinkage can be increased.If the heat-treating temperature is too high, operability of the processbecomes difficult because of frequent fiber breaks. It is preferred thatthe speeds of the heat-treating rolls and draw rolls be substantiallyequal in order to keep fiber tension substantially constant (for example0.2 cN/dtex or greater) at this point in the process and thereby avoidloss of fiber crimp.

An alternative arrangement of rolls and jets is illustrated in FIG. 7.Just-spun bicomponent fiber 6 can be passed by optional primary finishroll 10 a and optional interlace jet 20 a and then around feed rolls 13,which can be unheated. The fiber can be drawn through draw jet 21, whichcan be operated at pressures of 0.2-8.0 bar (2040-81,600 Kg/m²) andtemperatures of 180° C.-400° C., and both heat-treated and drawn byrolls 14, which can heat the fiber to a temperature of about 140°C.-185° C., preferably about 160° C.-175° C. The draw ratio used can bein the same range as described above for the arrangement shown in FIG.3. Fiber 6 can then be passed around optional roll 22 (optionallyoperated at speeds lower than rolls 14 in order to relax the fiber) inpreparation for optional interlacing by interlace jet 20 b, and can bepassed around optional roll 16 (to adjust the fiber tension forsatisfactory winding), past optional finish roll 10 b, and finally towindup 17.

Finally, the fiber is wound up. When cross-flow quench gas flow is used,the windup speed is at least about 3,300 meters per minute, preferablyat least about 4,000 meters per minute, and more preferably atabout.4,500-5,200 meters per minute. When co-current quench gas flow andone quench zone are used, the windup speed is at least about 3,300meters per minute, preferably at least about 4,500 meters per minute,and more preferably about 5,000-6,100 meters per minute. If co-currentquench gas flow and two quench zones are used, the windup speed is atleast about 3,300 meters per minute, preferably at least about 4,500meters per minute and more preferably about 5,000-8,000 meters perminute.

The wound fiber can be of any size, for example 0.5-20 denier perfilament (0.6-22 dtex per filament). It has now been found that novelpoly(ethylene terephthalate)//poly-(trimethylene terephthalate) fibersof about 0.5-1.5 denier per filament (about 0.6-1.7 dtex per filament)having a side-by-side or eccentric sheath core cross-section and asubstantially round, oval, or snowman cross-sectional shape can be madeat low, intermediate, or high spinning speeds. For high crimpcontraction levels, for example above about 30%, it is preferred thatsuch novel fibers have a weight ratio of poly(ethylene terephthalate) topoly(trimethylene terephthalate) in the range of about 30/70 to 70/30.It was unexpected that such fine fibers could reliably be drawnsufficiently to give such high crimp levels.

When a plurality of fibers of the invention are combined into a yarn,the yarn can be of any size, for example up to 1300 decitex. Any numberof filaments, for example 34, 58, 100, 150, or 200, can be spun usingthe process of the invention.

It was found unexpectedly that highly uniform bicomponent fibers,comprising two polymers that react differently to their environment asindicated by their spontaneous crimp, can be made with a low averagedecitex(denier) spread of less than about 2.5%, typically in the rangeof 1.0-2.0%. Uniform fibers are valuable because mill efficiency andprocessing are improved due to fewer fiber breaks, and fabrics made fromsuch fibers are visually uniform.

The process of the present invention can be operated as a coupledprocess or as a split process in which the bicomponent fiber is wound upafter the withdrawing step and later backwound for the hot-drawing andheat-treating steps. If a split process is used, the next steps areaccomplished without excessive delay, typically less than about 35 daysand preferably less than about 10 days, in order to achieve the desiredbicomponent fiber. That is, the drawing step is completed before theas-spun fiber becomes embrittled due to aging in order to avoidexcessive fiber breaks during drawing. Undrawn fiber can be storedrefrigerated, if desired, to diminish this potential problem. After thedrawing step, the heat-treating step is completed before the drawn fiberrelaxes significantly (typically in less than a second).

The weight ratio of the two polyesters in the bicomponent fibers made bythe process of the invention is about 30/70-70/30, preferably about40/60-60/40, and more preferably about 45/55-55/45.

The two polyesters used in the process of the present invention havedifferent compositions, for example 2G-T and 3G-T (most preferred) or2G-T and 4G-T and preferably have different intrinsic viscosities. Otherpolyesters include poly(ethylene 2,6-dinaphthalate, poly(trimethylene2,6-dinaphthalate), poly(trimethylene bibenzoate), poly(cyclohexyl1,4-dimethylene terephthalate), poly(1,3-cyclobutane dimethyleneterephthalate), and poly(1,3-cyclobutane dimethylene bibenzoate). It isadvantageous for the polymers to differ both with respect to intrinsicviscosity and composition, for example, 2G-T having an IV of about0.45-0.80 dl/g and 3G-T having an IV of about 0.85-1.50 dl/g, to achievean after heat-set crimp contraction value of at least 30%. When 2G-T hasan IV of about 0.45-0.60 dl/g and 3-GT has an IV of about 1.00-1.20dl/g, a preferred composition, after heat-set crimp contraction valuesof at least about 40% can be achieved. Nevertheless, the two polymersmust be sufficiently similar to adhere to each other; otherwise, thebicomponent fiber will split into two fibers.

One or both of the polyesters used in the process of the invention canbe copolyesters. For example, a copoly(ethylene terephthalate) can beused in which the comonomer used to make the copolyester is selectedfrom the group consisting of linear, cyclic, and branched aliphaticdicarboxylic acids having 4-12 carbon atoms (for example butanedioicacid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and1,4-cyclo-hexanedicarboxylic acid); aromatic dicarboxylic acids otherthan terephthalic acid and having 8-12 carbon atoms (for exampleisophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic,and branched aliphatic diols having 3-8 carbon atoms (for example1,3-propane diol, 1,2-propanediol, 1,4-butanediol,3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol,2-methyl-1,3-propanediol, and 1,4-cyclohexanediol); and aliphatic andaraliphatic ether glycols having 4-10 carbon atoms (for example,hydroquinone bis(2-hydroxyethyl) ether, or a poly(ethyleneether) glycolhaving a molecular weight below about 460, including diethyleneetherglycol). The comonomer can be present in the copolyester at levels ofabout 0.5-15 mole percent.

Isophthalic acid, pentanedioic acid, hexanedioic acid, 1,3-propane diol,and 1,4-butanediol are preferred because they are readily commerciallyavailable and inexpensive.

The copolyester(s) can contain minor amounts of other comonomers,provided such comonomers do not have an adverse affect on the amount offiber crimp or on other properties. Such other comonomers include5-sodium-sulfoisophthalate, at a level of about 0.2-5 mole percent. Verysmall amounts of trifunctional comonomers, for example trimellitic acid,can be incorporated for viscosity control.

As wound up, the bicomponent fiber made by the present process exhibitsconsiderable crimp. Some crimp may be lost on the package, but it can be“re-developed” upon exposure to heat in a substantially relaxed state.Final crimp development can be attained under dry heat or wet heatconditions. For example, dry or wet (steam) heating in a tenter frameand wet heating in a jig scour can be effective. For wet heating ofpolyester-based bicomponent fibers, a temperature of about 190° F. (88°C.) has been found useful. Alternatively, final crimp can be developedby a process disclosed in U.S. Pat. No. 4,115,989, in which the fiber ispassed with overfeed through a bulking jet with hot air or steam, thendeposited onto a rotating screen drum, sprayed with water, unraveled,optionally interlaced, and wound up.

In the Examples, the draw ratio applied was the maximum possible withoutgenerating a significant increase in the number and/or frequency ofbroken fibers and was typically at about 90% of break-draw. Unlessotherwise indicated, rolls 13 in FIG. 3 were operated at about 60° C.,rolls 14 at about 120° C. and rolls 15 at about 160° C.

Intrinsic viscosity (“IV”) of the polyesters was measured with aViscotek Forced Flow Viscometer Model Y-900 at a 0.4% concentration at19° C. and according to ASTM D-4603-96 but in 50/50 wt % trifluoroaceticacid/methylene chloride instead of the prescribed 60/40 wt %phenol/1,1,2,2-tetrachloroethane. The measured viscosity was thencorrelated with standard viscosities in 60/40 wt %phenol/1,1,2,2-tetrachloroethane to arrive at the reported intrinsicviscosity values. IV in the fiber was measured by exposing polymer tothe same process conditions as polymer actually spun into bicomponentfiber except that the test polymer was spun through a sampling spinneret(which did not combine the two polymers into a single fiber) and thencollected for IV measurement.

Unless otherwise noted, the crimp contraction in the bicomponent fibermade as shown in the Examples was measured as follows. Each sample wasformed into a skein of 5000±5 total denier (5550 dtex) with a skein reelat a tension of about 0.1 gpd (0.09 dN/tex). The skein was conditionedat 70±2° F. (21±1° C.) and 65±2% relative humidity for a minimum of 16hours. The skein was hung substantially vertically from a stand, a 1.5mg/den (1.35 mg/dtex) weight (e.g. 7.5 grams for a 5550 dtex skein) washung on the bottom of the skein, the weighted skein was allowed to cometo an equilibrium length, and the length of the skein was measured towithin 1 mm and recorded as “C_(b)”. The 1.35 mg/dtex weight was left onthe skein for the duration of the test. Next, a 500 gram weight (100mg/d; 90 mg/dtex) was hung from the bottom of the skein, and the lengthof the skein was measured to within 1 mm and recorded as “L_(b)”. Crimpcontraction value (percent) (before heat-setting, as described below forthis test), “CC_(b)”, was calculated according to the formulaCC _(b)=100×(L _(b) −C _(b))/L _(b)The 500-g weight was removed and the skein was then hung on a rack andheat-set, with the 1.35 mg/dtex weight still in place, in an oven for 5minutes at about 225° F. (107° C.), after which the rack and skein wereremoved from the oven and conditioned as above for two hours. This stepis designed to simulate commercial dry heat-setting, which is one way todevelop the final crimp in the bicomponent fiber. The length of theskein was measured as above, and its length was recorded as “C_(a)”. The500-gram weight was again hung from the skein, and the skein length wasmeasured as above and recorded as “La”. The after heat-set crimpcontraction value (%), “CC_(a)”, was calculated according to the formulaCC _(a)=100×(L _(a) −C _(a))/L _(a).CC_(a) is reported in the Tables. After-heat-set crimp contractionvalues obtained from this test are within this invention and acceptableif they are above about 30% and, preferably, above about 40%.

Decitex Spread (“DS”), a measure of the uniformity of a fiber, wasobtained by calculating the variation in mass at regular intervals alongthe fiber, using an ACW/DVA (Automatic Cut and Weigh/Decitex VariationAccessory) instrument (Lenzing Technik), in which the fiber was passedthrough a slot in a capacitor which responded to the instantaneous massof the fiber. The mass was measured every 0.5 m over eight 30-m lengthsof the fiber, the difference between the maximum and minimum mass withineach of the lengths was calculated and then averaged over the eightlengths, and the average difference divided by the average mass of theentire 240-m fiber length was recorded as a percentage. To obtain“average Decitex Spread”, such measurements were made on at least threepackages of fiber. The lower the DS, the higher the uniformity of thefiber.

In spinning the bicomponent fibers in Examples 1-4, the polymers weremelted with Werner & Pfleiderer co-rotating 28-mm extruders having0.5-40 pound/hour (0.23-18.1 kg/hour) capacities. The highest melttemperature attained in the 2G-T extruder was about 280-285° C., and thecorresponding temperature in the 3G-T extruder was about 265-275° C.Pumps transferred the polymers to the spinning head. In Examples 1-4,the fibers were wound up with a Barmag SW6 2s 600 winder (Barmag AG,Germany), having a maximum winding speed of 6,000 meters per minute.

The spinneret used in Examples 1-4 was a post-coalescence bicomponentspinneret having thirty-four pairs of capillaries arranged in a circle,an internal angle between each pair of capillaries of 30°, a capillarydiameter of 0.64 mm, and a capillary length of 4.24 mm. Unless otherwisenoted, the weight ratio of the two polymers in the fiber was 50/50.Total yarn decitex in Examples 1 and 2 was about 78.

EXAMPLE 1

A. 1,3-Propanediol (“3G”) was prepared by hydration of acrolein in thepresence of an acidic cation exchange catalyst, as disclosed in U.S.Pat. No. 5,171,898, to form 3-hydroxypropionaldehyde. The catalyst andany unreacted acrolein were removed by known methods, and the3-hydroxypropionaldehyde was then catalytically hydrogenated using aRaney Nickel catalyst (for example as disclosed in U.S. Pat. No.3,536,763). The product 1,3-propanediol was recovered from the aqueoussolution and purified by known methods.

B. Poly(trimethylene terephthalate) was prepared from 1,3-propanedioland dimethylterephthalate (“DMT”) in a two-vessel process usingtetraisopropyl titanate catalyst, Tyzor® TPT (a registered trademark ofE. I. du Pont de Nemours and Company) at 60 ppm, based on polymer.Molten DMT was added to 3G and catalyst at 185° C. in atransesterification vessel, and the temperature was increased to 210° C.while methanol was removed. The resulting intermediate was transferredto a polycondensation vessel where the pressure was reduced to onemillibar (10.2 kg/cm²), and the temperature was increased to 255° C.When the desired melt viscosity was reached, the pressure was increasedand the polymer was extruded, cooled, and cut into pellets. The pelletswere further polymerized in a solid-phase to an intrinsic viscosity of1.04 dl/g in a tumble dryer operated at 212° C.

C. Poly(ethylene terephthalate) (Crystar® 4415, a registered trademarkof E. I. du Pont de Nemours and Company), having an intrinsic viscosityof 0.54 dl/g, and poly(trimethylene terephthalate), prepared as in stepB above, were spun using the apparatus of FIG. 2. The spinnerettemperature was maintained at about 272° C. In the spinning apparatus,the internal diameter of cylindrical screen 5 was 4.0 inches (10.2cm),the length B of screen 5 was 6.0 inches (15.2cm), the diameter of cone 8at its widest was 4.0 inches (10.2cm), the length of cone C2 was 3.75inches (9.5cm), the length of tube C3 was 15 inches (38.1cm), and thedistance C1 was 0.75 inch (1.9 cm). The inner diameter of tube 8 was 1.0inch (2.5 cm), and the (post-coalescence) spinneret was recessed intothe top of the spinning column by 4 inches (10.2 cm) (“A” in FIG. 2) sothat the quench gas contacted the just-spun fibers only after a delay.The quench gas was air, supplied at a room temperature of about 20° C.The fibers had a side-by-side cross-section and an oval cross-sectionalshape.

About 10 wraps were taken around the heat-treating rolls. TABLE I AirAir Withdrawal Speed/ Windup Speed (1) Speed Withdrawal Draw SpeedCC_(a) Sample (mpm) (mpm) Speed Ratio (mpm) (%) 1 560 875 0.6 4.0 350051 2 560 1000 0.6 4.0 4000 55 3 560 1125 0.6 4.0 4500 57 4 1141 1250 0.94.0 4975 54 5 906 1250 0.7 4.0 5000 54 6 1141 1336 0.9 3.7 4975 54 71472 1388 1.1 3.6 4940 51 8 1472 1571 0.9 3.5 5440 51 9 1695 1714 1.03.5 5930 44(1) In the 2.54-cm inner diameter tube fiber exitThe data show that good crimp can be attained at high withdrawal andwindup speeds using the process of the invention and two polyesters. Thedata also suggest that windup speeds of up to at least about 6,100meters per minute can be successfully used in the present co-current gasflow process when one co-current quench zone is used (see curve “1” inFIG. 5, which shows an extrapolation of windup speed).

EXAMPLE 2

Crystar® 4415 and poly(trimethylene terephthalate) as prepared inExample 1 were spun into a side-by-side oval bicomponent fiber using thecross-flow quench apparatus of FIG. 1. The spinneret temperature wasmaintained at about 272° C. For samples 10-15, the (post-coalescence)spinneret was recessed into the top of the spinning column by six inches(15.2 cm) (“A” in FIG. 1). The height of the zone below the spinneret(“2” in FIG. 1 was 172 cm. For samples 10-13, the flow of quench air hadthe following profile, measured 5 inches (12.7 cm) from screen 5 (seeFIG. 1): Distance below Air speed spinneret (cm) (mpm) 15 8.5 30 9.4 469.4 61 11.0 76 11.0 91 11.3 107 11.6 122 16.5 137 34.1 152 39.6 168 29.6For samples 14 and 15, the quench air velocity was approximately 50%higher.

For samples 16 and 17, no recess (no heated quench delay space) wasused, and the quench air flow had the following profile, also measured 5inches (12.7 cm) from screen 5: Distance below Air spinneret speed (cm)(mpm) 2.5 15.2 30.5 12.2 61.0 11.3 91.4 9.8 121.9 9.8 152.4 9.8

Properties of the resulting fibers are given in Table II and illustratedas curve “2” in FIG. 2. The data show that high crimp levels can beobtained at surprisingly high speeds with crossflow quench gas. Aboveabout 3,500 mpm feed roll speed (withdrawal speed), fiber breaksprevented the application of sufficient draw to attain high crimpcontraction levels. TABLE II Withdrawal Windup Speed Draw Speed CC_(a)Sample (mpm) Ratio (mpm) (%) 10 750 4.0 2980 56 11 933 3.7 3470 57 121176 3.4 3960 51 13 1406 3.2 4455 53 14 2000 2.4 4750 45 15 3250 1.65150 45 16 4417 1.2 5250 13 17 4818 1.1 5270 2

EXAMPLE 3

Using the same spinning equipment as employed in Example 1,poly(ethylene terephthalate) and poly(trimethylene terephthalate),prepared as in Example 1, side-by-side oval cross-section bicomponentyarns of 34 filaments and 49-75 dtex (1.4-2.2 dtex per filament) werespun at withdrawal speeds of 2,800-4,500 meters per minute. The fiberswere wound up on bobbins without drawing. The fibers were stored at roomtemperature (about 20° C.) for about three weeks and at about 5° C. forabout fifteen days, after which they were drawn over a 12-inch (30 cm)hot shoe held at 90° C. at a feed roll speed of 5-10 meters per minuteand heat-treated by passing them at constant length through a 12-inch(30 cm) glass tube oven held at 160° C. The fibers were drawn at 90% ofthe draw at which they broke. In this Example, crimp contraction levelswere measured immediately after drawing and heat-treating by hanging aloop of fiber from a holder with a 1.5 mg/denier (1.35 mg/dtex) weightattached to the bottom of the loop and measuring the length of the loop.Then a 100 mg/den (90 mg/dtex) weight was attached to the bottom of theloop, and the length of the loop was measured again. Crimp contractionwas calculated as the difference between the two lengths, divided by thelength measured with the 90 mg/dtex weight. This method gives crimpcontraction values up to about 10% (absolute) higher than the methoddescribed for “CC_(a)” so that values above about 40% are acceptable.Results are summarized in Table III. TABLE III Air Air Withdrawal Speed/Crimp Speed (1) Speed Withdrawal Draw Contraction Sample (mpm) (mpm)Speed Ratio (%) 18 1200 2800 0.43 2.0 50 19 1515 3500 0.43 1.6 42 201712 4000 0.43 1.4 51 21 — 4500 — 1.2 19(1) In the 2.54-cm inner diameter tube fiber exit

The results showed that, after spinning, drawing can be delayed by aboutfive weeks (for example, in a split process) and still be effective ingenerating crimp in bicomponent fibers spun with co-current air flow andthat useful crimp levels can be attained with draw ratios as low asabout 1.4.

EXAMPLE 4

The same apparatus and polymers as in Example 1 were used, but with anunheated quench delay space (created by an unheated cylinder coaxialwith the spinneret) of 2 inches (5.1 cm). The withdrawal speed was 2,000m/min, the draw ratio was 2.5-2.6, and the windup speed was 5,000-5,200m/min. Oval side-by-side bicomponent fibers were produced with singlesuperatmospheric quench zone pressures so that the corresponding airspeeds at exit 7 of tube 8 (see FIG. 2) were 1141 m/min and 1695 m/min,respectively. The resulting 2G-T//3G-T bicomponent yarns of 34 filamentsand 42 decitex (38 denier) [1.1 denier (1.2 dtex) per filament] hadunexpectedly high crimp contraction (“CCa”) levels, 49-62%, which werecomparable to crimp levels obtained in Example 1 for filament of nearlytwice the dtex/filament. At this low decitex, higher speeds were notpossible with this apparatus geometry and process conditions, due tobreaks in the fibers during drawing and heat-treating and on the woundpackage. However, when the cylinder creating the 2-inch (5.1 cm) quenchdelay space was heated with a band heater at 250° C. and the position oftube 8 (see FIG. 2) was raised so that distance “C1” in FIG. 2 wasreduced substantially to zero, even finer 2G-T//3G-T bicomponent yarnsof 38 decitex (34 denier) and 34 filaments [1.0 denier(1.1 dtex) perfilament] and having good crimp contraction (“CCa”) levels (40-49%) wereproduced at up to 5,700 m/min with a draw ratio of 2.85. Thus, heatingthe quench delay space and shortening the quench zone improved highspeed process continuity for very fine polyester bicomponent fibers.Knit and woven and woven fabrics prepared from these filaments had avery soft hand.

EXAMPLE 5

This example illustrates the use of a two-zone co-current quench under avariety of conditions. In each of Examples 5A, 5B, and 5C, poly(ethyleneterephthalate) (Crystar® 4415-675) having an intrinsic viscosity of 0.52dl/g, and poly(trimethylene terephthalate) prepared as in step B ofExample 1, were spun into 34 side-by-side bicomponent filaments usingthe spinning apparatus of FIG. 4 and the roll-and-jet arrangement ofFIG. 7. The extruder used for 2G-T was a single-screw Barmag model4E10/24D with a 4E4-41-2042 model screw. The extruder used for 3G-T wasa single-screw Barmag Maxflex (single zone heating, 30 mm internaldiameter) with a MAF30-41-3 model single flight screw. The residencetimes in the transfer lines between the extruder discharge and thespinneret face were measured by adding briefly dye chips to the polymersand determining the time it took for the dye to appear in, and thendisappear from, the fiber. For the 2G-T line, the appearance time was 6½minutes, and the disappearance time was over 40 minutes. For the 3G-Tline, the appearance time was 4¾ minutes, and the disappearance time was10 minutes. The poly(tri-methylene terephthalate) was discharged fromthe extruder at a temperature less than about 260° C. and the transferline was at about the same temperature. The angle between thecapillaries in the post-coalescence spinneret was 3°, and the distancebetween the capillaries at their exits was 0.067 mm. The pre-coalescencespinneret had a combined capillary and counterbore length of 16.7 mm.The quench gas entered the spinning column at least 90 mm below thespinneret (“A” in FIG. 4) so that the gas first contacted the just-spunfibers only after a delay; the recess was not intentionally heated. Thequench gas was air, supplied at a temperature of 20° C. and a relativehumidity of 65%. The minimum inner diameter of tube 8 a was 0.75 inch(1.91 cm) and the minimum inner diameter of tube 8 b was 1.5 inch (3.81cm). Five-and-a-half wraps were taken around unheated feed rolls 13.Draw jet 21 was operated at 0.6 bar (6118 Kg/cm²) and 225° C., and thesteam flow was adjusted to control the position of the drawpoint. Drawrolls 14 also functioned as heat-treating rolls and were operated at180° C.; five-and-a-half wraps were taken around these rolls, too. Thewinder was a commercial Barmag CRAFT 8-end winder capable of 7000 m/minwinding speed. The fibers had a side-by-side cross-section, and thetotal yarn denier was 96 in Examples 5A and 5C and 108 in Example 5B(107 decitex and 120 decitex, respectively). Other spinning conditionsand the cross-sectional shapes and crimp contraction levels aresummarized in Table IV. TABLE IV Example 5A 5B 5C Polymer Weight Ratio60/40 50/50 45/55 (2G-T//3G-T) 2G-T Transfer Line(° C. 278 263 278Spinneret Type Post- Pre- Post- Coalescence Coalescence Coalescence SpinBlock(° C.) 278 263 278 1st Quench Zone Max. 3180 3180 3180 Air Speed(m/min) 2nd Quench Zone Max. 2152 2184 2152 Air Speed (m/min) Feed Rolls13 Speed 2715 2100 2870 (m/min) Draw Rolls 14 Speed 6810 6835 6833(m/min) Draw Ratio 2.5 3.2 2.4 Roll 22 Speed (mpm) 6810 6835 6833 Roll16 Speed (mpm) 6770 6775 6793 Winder 17 Speed (mpm) 6702 6710 6700 FiberCross-sectional Snowman Round Snowman Shape CC_(a), % 55 67 58The decitex spread for Example 5B, based on data from a single package,was 1.36%. The data in Table IV show that very high crimp levels can beattained at very high speeds by using the process of the invention.

EXAMPLE 6

This example relates to novel, highly uniform bicomponent fiberscomprising poly(ethylene terephthalate) and poly(trimethyleneterephthalate) The polymers, extruders, spinning apparatus, spinneretrecess, quench gas, winder, and roll-and-jet arrangement used were thesame as in Example 5. The post-coalescence spinneret of Example 5 wasused, and the fiber cross-sectional shape in each case was “snowman”.The temperature of the poly(trimethylene terephthalate) as it left theextruder was less than about 260° C., and the transfer line was at aboutthe same temperature. The recess was not intentionally heated except inExample 6.C, in which it was heated to 120° C. Feed rolls 13 were notintentionally heated except in Example 6.B., in which they were heatedto 55° C. The steam flow in draw jet 21 was adjusted to control thelocation of the drawpoint. Draw rolls 14 also functioned asheat-treating rolls and were again operated at 180° C. Five-and-a-halfwraps were taken around the feed rolls and draw rolls. Other spinningconditions and crimp contraction levels are given in Table V. DecitexSpread data are presented in Table VI. TABLE V Example 6A 6B 6C Decitex174 172 82 Number of filaments 68 34 34 Polymer Weight Ratio 60/40 50/5050/50 (2G-T//3-GT) 2G-T transferline (Dowtherm 264 262 280 temp. ° C.)Spin block (Dowtherm temp., ° C.) 264 262 280 1st Quench Zone Max. AirSpeed 3079 3180 2980 (m/min) 2nd Quench Zone Max. Air Speed 1895 21841766 (m/min) Steam draw jet pressure (kg/m²) 7134 29,572 5099 Steam drawjet temp. (° C.) 237 240 224 Feed Rolls 13 speed (m/min) 1915 2140-22101300-1380 Draw Rolls 14 speed (m/min) 6123 6845 4300 Draw Ratio 3.23.1-3.2 3.1-3.3 Roll 22 Speed (m/min) 6123 6845 4300 Roll 16 Speed(m/min) 6081 6775 4275 Winder 17 Speed (m/min) 6001 6710 4200 CrimpContraction (“CC_(a)”), % 57 55 56

TABLE VI Example Package DS(%) 6A 1 1.8 2 2.2 3 2.0 4 2.1 5 1.9 Average2.0 6B 1 1.9 2 2.1 3 1.8 Average 1.9 6C 1 1.3 2 1.8 3 1.7 4 1.8 Average1.6

EXAMPLE 7 (COMPARISON)

This Example shows what levels of uniformity can be obtained usingconventional cross-flow quench in making polyester bicomponent fibers.Poly(trimethylene terephthalate) containing 0.3 wt % TiO2 and preparedas described in Example 1 but having an IV of 1.02-1.06, andpoly(ethylene terephthalate) (Crystar® 4415, IV 0.52) were used. Thepolymers were melted in independent extruders and separately transportedto a pre-coalescence spinneret at a melt temperature of 256° C. (3G-T)or 285° C. (2G-T). In the fibers, the 3G-T IV was about 0.93, and the3G-T IV was about 0.52. The weight ratio of 2G-T to 3G-T was 41/59. Theextruded bicomponent multifilament yarn was cooled in a cross flowquench unit using an air speed of 16 m/min, supplied from a plenumthrough a vertical diffuser screen. The roll-and-jet arrangement of FIG.9 was used. 5 wt % (based on fiber) of an ester-based finish was applied2 meters below spinneret face 3 (see FIG. 9) by an applicator not shown.Yarn 6 was passed 2.5 times around feed roll 13 and associated separatorroll 13 a, through steam draw jet 21 (operated at 180° C.) and thenaround draw roll 14 and associated separator roll 14 a. The yarn wasthen drawn a second time between draw roll 14 and pair of rolls 15 inhot chest 76, which was heated to 170° C. A total of 7.5 wraps weretaken around the two hot chest rolls. The yarn was passed around roll22, through dual interlace jets 20, and then around roll 16. The samefinish was reapplied at finish applicator 10, again at the same 5 wt %.Finally, the yarn was wound onto a paper core tube at windup 17. Theroll and windup speeds (in meters/minute) are summarized in Table VII,and the resulting average Decitex Spreads are reported in Table VIII.TABLE VII Example 7A 7B 7C Yarn decitex 167 167 83 Number of filaments68 34 34 Speeds, m/min: Feed roll 13 840 325 840 Draw roll 14 2560 10522560 Hot chest rolls 15 3110 1495 3110 Roll 22 2970 1480 2970 Roll 162912 1429 2912 Windup 17 2876 1413 2876 Total draw ratio 3.7 4.6 3.7

TABLE VIII Example Package DS(%) 7A 1 2.2 (1) 2 3.1 3 2.9 4 2.9 5 3.2 63.0 Average 2.9 7B 1 3.9 2 2.9 3 3.7 4 3.4 5 3.6 6 2.6 Average 3.3 7C 13.5 2 2.7 3 3.0 4 2.8 5 3.0 Average 3.0(1)The decitex spread for Example 7A, Package 1 is a statistical outlierand believed not to be representative of the true value of decitexspread in polyester bicomponent fibers obtained with conventional quenchmethods, as evidenced by the high average Decitex Spread obtained inExample 7A.

Comparison of the results for Examples 6 and 7 shows that unusuallyuniform 2G-T//3G-T bicomponent fibers can now be made.

1-26. (canceled)
 27. A process for preparing a bicomponent fibercomprising the steps of: (a) providing poly(trimethylene terephthalate)and a polyester selected from the group consisting of poly(ethyleneterephthalate) and a copolyester of poly(ethylene terephthalate) havingdifferent intrinsic viscosities; (b) melt-spinning the two polyestersfrom a spinneret to form at least one bicomponent fiber having across-section selected from the group consisting of side-by-side andeccentric sheath-core; (c) providing at least one flow of gas to atleast one quench zone below the spinneret and accelerating the flow to amaximum velocity in the direction of fiber travel; (d) passing the fiberthrough the quench zone; (e) withdrawing the fiber at a withdrawal speedin the range of about: 820 to 4,000 meters per minute when co-currentquench gas flow is used, and in the range of about 1,000 to 3,000 metersper minute when cross or radial quench gas flow is used; and (f) windingup the fiber without drawing.
 28. The process of claim 27 furthercomprising, after step (f), the steps of: (g) drawing; and (h)heat-treating the fibers.
 29. The process of claim 28, wherein thefibers have, after step (h), an after-heat-set crimp contraction valueof at least about 30%.
 30. The process of claim 28, wherein step (g)follows step (f) by less than about 35 days.